Adding DynamicallySizableImageDataProvider Interface

Implementations of DynamicallySizableImageDataProvider can provide image
data at a requested targetHeight and targetWidth. The behavior of
GC#drawImage() is updated: when drawing a dynamically sizeable image, it
requests a handle at the target size. If the image can be loaded at that
size, it is used directly; otherwise, the image is loaded as before and
scaled using zoom.

In the Windows implementation, if the source or destination width/height
is set to zero, the image will be drawn fully, avoiding the need to call
getBounds() to determine the image size.

Author: arunjose696

bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/graphics/Image.java

@@ -1820,11 +1820,12 @@ public String toString () {
  * @param imageData the imageData which is used to draw the scaled Image
  * @param width the width of the original image
  * @param height the height of the original image
- * @param scaleFactor the factor with which the image is supposed to be scaled
+ * @param targetWidth the width to which the image is supposed to be scaled
+ * @param targetHeight the height to which the image is supposed to be scaled
  *
  * @noreference This method is not intended to be referenced by clients.
  */
-public static void drawScaled(GC gc, ImageData imageData, int width, int height, float scaleFactor) {
+public static void drawAtTargetSize(GC gc, ImageData imageData, int width, int height, int targetWidth, int targetHeight) {
 	StrictChecks.runWithStrictChecksDisabled(() -> {
 		Image imageToDraw = new Image(gc.device, (ImageDataProvider) zoom -> imageData);
 		gc.drawImage(imageToDraw, 0, 0, CocoaDPIUtil.pixelToPoint(width), CocoaDPIUtil.pixelToPoint(height),
@@ -1833,8 +1834,7 @@ public static void drawScaled(GC gc, ImageData imageData, int width, int height,
 				 * avoiding rounding errors. Nevertheless, we still have some rounding errors
 				 * due to the point-based API GC#drawImage(..).
 				 */
-				0, 0, Math.round(CocoaDPIUtil.pixelToPoint(width * scaleFactor)),
-				Math.round(CocoaDPIUtil.pixelToPoint(height * scaleFactor)));
+				0, 0, targetWidth, targetHeight);
 		imageToDraw.dispose();
 	});
 }

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/graphics/ImageDataAtSizeProvider.java

@@ -0,0 +1,22 @@
+/*******************************************************************************
+ * Copyright (c) 2025 Vector Informatik GmbH and others.
+ *
+ * This program and the accompanying materials are made available under the terms of the Eclipse
+ * Public License 2.0 which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Michael Bangas (Vector Informatik GmbH) - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.swt.graphics;
+
+/**
+ * @since 3.132
+ */
+public interface ImageDataAtSizeProvider extends ImageDataProvider {
+
+	ImageData getImageData(int targetWidth, int targetHeight);
+
+}

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/graphics/ImageDataLoader.java

@@ -45,6 +45,14 @@ public static boolean canLoadAtZoom(String filename, int fileZoom, int targetZoo
 		return ImageLoader.canLoadAtZoom(filename, fileZoom, targetZoom);
 	}
 
+	static boolean isDynamicallySizable(String filename) {
+		return ImageLoader.isDynamicallySizable(filename);
+	}
+
+	static boolean isDynamicallySizable(InputStream stream) {
+		return ImageLoader.isDynamicallySizable(stream);
+	}
+
 	public static ElementAtZoom<ImageData> loadByZoom(InputStream stream, int fileZoom, int targetZoom) {
 		List<ElementAtZoom<ImageData>> data = new ImageLoader().loadByZoom(stream, fileZoom, targetZoom);
 		if (data.isEmpty()) SWT.error(SWT.ERROR_INVALID_IMAGE);

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/graphics/ImageLoader.java

@@ -229,6 +229,19 @@ static boolean canLoadAtZoom(String filename, int fileZoom, int targetZoom) {
 	return false;
 }
 
+static boolean isDynamicallySizable(String filename) {
+	try (InputStream stream = new FileInputStream(filename)) {
+		return FileFormat.isDynamicallySizableFormat(stream);
+	} catch (IOException e) {
+		SWT.error(SWT.ERROR_IO, e);
+	}
+	return false;
+}
+
+static boolean isDynamicallySizable(InputStream stream) {
+	return FileFormat.isDynamicallySizableFormat(stream);
+}
+
 /**
  * Saves the image data in this ImageLoader to the specified stream.
  * The format parameter can have one of the following values:

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/internal/DPIUtil.java

@@ -146,14 +146,24 @@ public static ImageData autoScaleImageData (Device device, final ImageData image
 	int height = imageData.height;
 	int scaledWidth = Math.round (width * scaleFactor);
 	int scaledHeight = Math.round (height * scaleFactor);
+	return scaleImage(device, imageData, Image::drawAtTargetSize, width, height, scaledWidth, scaledHeight);
+}
+
+@FunctionalInterface
+private interface ImageDrawFunction {
+	void draw(GC gc, ImageData imageData, int originalWidth, int originalHeight, int targetWidth, int targetHeight);
+}
+
+private static ImageData scaleImage(Device device, final ImageData imageData, ImageDrawFunction drawFunction, int width, int height,
+		int scaledWidth, int scaledHeight) {
 	int defaultZoomLevel = 100;
 	boolean useSmoothScaling = isSmoothScalingEnabled() && imageData.getTransparencyType() != SWT.TRANSPARENCY_MASK;
 	if (useSmoothScaling) {
 		ImageGcDrawer drawer =  new ImageGcDrawer() {
 			@Override
 			public void drawOn(GC gc, int imageWidth, int imageHeight) {
 				gc.setAntialias (SWT.ON);
-				Image.drawScaled(gc, imageData, width, height, scaleFactor);
+				drawFunction.draw(gc, imageData, width, height, imageWidth, imageHeight);
 			};
 
 			@Override
@@ -170,6 +180,10 @@ public int getGcStyle() {
 	}
 }
 
+public static ImageData autoScaleImageData(Device device, final ImageData imageData, int targetWidth, int targetHeight) {
+	return scaleImage(device, imageData, Image::drawAtTargetSize, imageData.width, imageData.height, targetWidth, targetHeight);
+}
+
 public static boolean isSmoothScalingEnabled() {
 	return autoScaleMethod == AutoScaleMethod.SMOOTH;
 }

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/internal/image/FileFormat.java

@@ -73,7 +73,16 @@ private static Optional<FileFormat> determineFileFormat(LEDataInputStream stream
 	private static final int MAX_SIGNATURE_BYTES = 18 + 2; // e.g. Win-BMP or OS2-BMP plus a safety-margin
 
 	public static boolean isDynamicallySizableFormat(InputStream is) {
-		Optional<FileFormat> format = determineFileFormat(new LEDataInputStream(is, MAX_SIGNATURE_BYTES));
+		if (!is.markSupported()) {
+	        is = new BufferedInputStream(is);
+	    }
+		is.mark(MAX_SIGNATURE_BYTES);
+	    Optional<FileFormat> format = determineFileFormat(new LEDataInputStream(is, MAX_SIGNATURE_BYTES));
+	    try {
+			is.reset();
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
 		return format.isPresent() && !(format.get() instanceof StaticImageFileFormat);
 	}
 

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Image.java

@@ -1581,11 +1581,12 @@ public String toString () {
  * @param imageData the imageData which is used to draw the scaled Image
  * @param width the width of the original image
  * @param height the height of the original image
- * @param scaleFactor the factor with which the image is supposed to be scaled
+ * @param targetWidth the width to which the image is supposed to be scaled
+ * @param targetHeight the height to which the image is supposed to be scaled
  *
  * @noreference This method is not intended to be referenced by clients.
  */
-public static void drawScaled(GC gc, ImageData imageData, int width, int height, float scaleFactor) {
+public static void drawAtTargetSize(GC gc, ImageData imageData, int width, int height, int targetWidth, int targetHeight) {
 	StrictChecks.runWithStrictChecksDisabled(() -> {
 		Image imageToDraw = new Image(gc.device, (ImageDataProvider) zoom -> imageData);
 		gc.drawImage(imageToDraw, 0, 0, width, height,
@@ -1594,7 +1595,7 @@ public static void drawScaled(GC gc, ImageData imageData, int width, int height,
 				 * avoiding rounding errors. Nevertheless, we still have some rounding errors
 				 * due to the point-based API GC#drawImage(..).
 				 */
-				0, 0, Math.round(width * scaleFactor), Math.round(height * scaleFactor));
+				0, 0, targetWidth, targetHeight);
 		imageToDraw.dispose();
 	});
 }

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/GC.java

@@ -1053,7 +1053,8 @@ void apply() {
 
 	private void drawImageInPixels(Image image, Point location) {
 		if (image.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
-		drawImage(image, 0, 0, -1, -1, location.x, location.y, -1, -1, true, getZoom());
+		long handle = Image.win32_getHandle(image, getZoom());
+		drawImage(image, 0, 0, -1, -1, location.x, location.y, -1, -1, true, handle);
 	}
 }
 
@@ -1091,7 +1092,10 @@ private void drawImageInPixels(Image image, Point location) {
  */
 public void drawImage (Image image, int srcX, int srcY, int srcWidth, int srcHeight, int destX, int destY, int destWidth, int destHeight) {
 	checkNonDisposed();
-	if (srcWidth == 0 || srcHeight == 0 || destWidth == 0 || destHeight == 0) return;
+	if (image == null && (srcWidth == 0 || srcHeight == 0)) return;
+	// Skip drawing only if exactly one source dimension is zero
+	if ((srcWidth == 0) ^ (srcHeight == 0)) return;
+	if (destWidth == 0 || destHeight == 0) return;
 	if (srcX < 0 || srcY < 0 || srcWidth < 0 || srcHeight < 0 || destWidth < 0 || destHeight < 0) {
 		SWT.error (SWT.ERROR_INVALID_ARGUMENT);
 	}
@@ -1156,8 +1160,8 @@ private int calculateZoomForImage(int gcZoom, int srcWidth, int srcHeight, int d
 private void drawImage(Image image, int srcX, int srcY, int srcWidth, int srcHeight, int destX, int destY,
 		int destWidth, int destHeight, int imageZoom, int scaledImageZoom) {
 	Rectangle src = Win32DPIUtils.pointToPixel(drawable, new Rectangle(srcX, srcY, srcWidth, srcHeight), scaledImageZoom);
-	Rectangle dest = Win32DPIUtils.pointToPixel(drawable, new Rectangle(destX, destY, destWidth, destHeight), imageZoom);
-	if (scaledImageZoom != 100) {
+	Rectangle destPixels = Win32DPIUtils.pointToPixel(drawable, new Rectangle(destX, destY, destWidth, destHeight), imageZoom);
+	if (scaledImageZoom % 100 != 0) {
 		/*
 		 * This is a HACK! Due to rounding errors at fractional scale factors,
 		 * the coordinates may be slightly off. The workaround is to restrict
@@ -1174,7 +1178,46 @@ private void drawImage(Image image, int srcX, int srcY, int srcWidth, int srcHei
 			}
 		}
 	}
-	drawImage(image, src.x, src.y, src.width, src.height, dest.x, dest.y, dest.width, dest.height, false, scaledImageZoom);
+	int targetWidth;
+	int targetHeight;
+	Rectangle scaledSrc;
+	if (srcWidth == 0 && srcHeight == 0) {
+		scaledSrc = new Rectangle(srcX, srcY, srcWidth, srcHeight);
+		targetWidth = destWidth;
+		targetHeight = destHeight;
+	} else {
+		float widthScalingFactor = (float) destWidth / srcWidth;
+		float heightScalingFactor = (float) destHeight / srcHeight;
+		Rectangle fullImageBounds = image.getBounds();
+		targetWidth = Math.round(fullImageBounds.width * widthScalingFactor);
+		targetHeight = Math.round(fullImageBounds.height * heightScalingFactor);
+
+		scaledSrc = new Rectangle(Math.round(src.x * widthScalingFactor),
+				Math.round(src.y * heightScalingFactor), Math.round(src.width * widthScalingFactor),
+				Math.round(src.height * heightScalingFactor));
+	}
+	Point targetSize = Win32DPIUtils.pointToPixel(drawable, new Point(targetWidth, targetHeight), scaledImageZoom);
+	image.executeOnImageHandleAtSizeOrZoom((tempHandle, handleSize) -> {
+		Rectangle srcRect = computeSourceRectangle(handleSize, targetSize, scaledSrc, src);
+		drawImage(image, srcRect.x, srcRect.y, srcRect.width, srcRect.height, destPixels.x, destPixels.y, destPixels.width,
+				destPixels.height, false, tempHandle);
+	}, targetSize.x, targetSize.y, scaledImageZoom);
+}
+
+/**
+ * Selects the source rectangle for drawing. If the requested width matches the image size,
+ * uses the scaled rectangle, otherwise the unscaled one.
+ */
+private Rectangle computeSourceRectangle(Point imageSize, Point requestedSize, Rectangle scaledSrc,
+		Rectangle unScaledSrc) {
+
+	Rectangle src = ((imageSize.x == requestedSize.x) && (imageSize.y == requestedSize.y)) ? scaledSrc : unScaledSrc;
+	// If both width and height are zero, use the full image
+	// (avoids forcing a getBounds() call inside drawImage)
+	if (src.width == 0 && src.height == 0) {
+		return new Rectangle(0, 0, imageSize.x, imageSize.y);
+	}
+	return src;
 }
 
 private class DrawImageToImageOperation extends ImageOperation {
@@ -1191,18 +1234,20 @@ private class DrawImageToImageOperation extends ImageOperation {
 
 	@Override
 	void apply() {
-		drawImage(getImage(), source.x, source.y, source.width, source.height, destination.x, destination.y, destination.width, destination.height, simple, getZoom());
+		long handle = Image.win32_getHandle(getImage(), getZoom());
+		drawImage(getImage(), source.x, source.y, source.width, source.height, destination.x, destination.y, destination.width, destination.height, simple, handle);
 	}
 }
 
-private void drawImage(Image srcImage, int srcX, int srcY, int srcWidth, int srcHeight, int destX, int destY, int destWidth, int destHeight, boolean simple, int imageZoom) {
+private void drawImage(Image srcImage, int srcX, int srcY, int srcWidth, int srcHeight, int destX, int destY, int destWidth, int destHeight, boolean simple, long tempImageHandle) {
 	if (data.gdipGraphics != 0) {
 		//TODO - cache bitmap
-		long [] gdipImage = srcImage.createGdipImage(imageZoom);
+		long [] gdipImage = srcImage.createGdipImageFromHandle(tempImageHandle);
+		BITMAP bm = new BITMAP();
+		OS.GetObject(tempImageHandle, BITMAP.sizeof, bm);
 		long img = gdipImage[0];
 		int imgWidth = Gdip.Image_GetWidth(img);
 		int imgHeight = Gdip.Image_GetHeight(img);
-
 		if (simple) {
 			srcWidth = destWidth = imgWidth;
 			srcHeight = destHeight = imgHeight;
@@ -1253,13 +1298,13 @@ private void drawImage(Image srcImage, int srcX, int srcY, int srcWidth, int src
 		}
 		return;
 	}
-	long imageHandle = srcImage.getHandle(imageZoom, data.nativeZoom);
 	switch (srcImage.type) {
 		case SWT.BITMAP:
-			drawBitmap(srcImage, imageHandle, srcX, srcY, srcWidth, srcHeight, destX, destY, destWidth, destHeight, simple);
+			drawBitmap(srcImage, tempImageHandle, srcX, srcY, srcWidth, srcHeight, destX, destY, destWidth, destHeight,
+					simple);
 			break;
 		case SWT.ICON:
-			drawIcon(imageHandle, srcX, srcY, srcWidth, srcHeight, destX, destY, destWidth, destHeight, simple);
+			drawIcon(tempImageHandle, srcX, srcY, srcWidth, srcHeight, destX, destY, destWidth, destHeight, simple);
 			break;
 	}
 }